Polycrystalline silicon is a material including multiple small silicon crystals, and has long been used as the conducting gate material in metal-oxide-semiconductor field-effect transistor (MOSFET) and complementary metal-oxide semiconductor (CMOS) processing technologies. It is usually fabricated by low-pressure chemical-vapour deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), or solid-phase crystallization (SPC) of amorphous silicon (a-Si:H). However, these processes require relatively high temperatures.
The aluminum-induced crystallization (AIC) of amorphous silicon (a-Si:H) has great potential for various applications, such as thin film transistors, sensors, solar cells, and display panels [1-3]. The presence of aluminum in contact with a-Si:H can significantly reduce the temperature at which a-Si:H can be crystallized [4-8], which may gain great relevance in photoelectronic and photovoltaic devices where low temperature processes are critical. The performance of devices fabricated using polycrystalline silicon strongly depends on grain sizes in the polycrystalline silicon because grain boundaries normally act as traps and recombination centers for carriers [9, 10]. Therefore, great attention has been drawn to increasing the average grain size of the polycrystalline silicon. For example, J. H. Oh obtained grain sizes of 104 μm after 580° C. annealing, using Ni mediated crystallization of amorphous silicon [13]. Although how to grow large size grains has been extensively investigated [11, 12], no one has reported a method of using the AIC technique to grow continuous and smooth highly doped polycrystalline silicon films with very large grains at low temperatures.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.